Senator Specter has changed parties because it was the only route to staying in the Senate. Senate Democrats reportedly are promising to let him transfer his seniority to the Democratic Caucus. The DSCC and Pennsylvania Democratic leaders (Ed Rendell) seem poised to discourage primary opposition to Senator Specter. Yet Specter is very conservative for a Democrat, and seems likely to remain so. (See Nate Silver.)
Senator Specter intends to remain his own cantankerous independent self. But especially given that the Senate over-represents rural America to the point that representatives of 10% of US voters can frustrate the will of the majority of Americans, it is just and right for Senator Specter to provide an automatic vote for cloture on all Democratic measures, even where he intends to vote against the underlying action.